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The California CORS Program
Yehuda Bock
Director, California Spatial Reference Center
Cecil H. and Ida M. Green Institute of
Geophysics and Planetary Physics
Scripps Institution of Oceanography
La Jolla, California
CORS Users Forum
National Geodetic Survey, NOAA/NOS
Silver Spring, Maryland
April 19, 2002
Current State of CORS in California
CORS in North America CORS in California and Nevada
Y. Bock, CORS Users Forum, April 19, 2002
Current State of CORS in California
Bay Area Regional Deformation
Array (BARD) - 50 stations
Southern California Integrated GPS
Network (SCIGN) - 250 stations
Y. Bock, CORS Users Forum, April 19, 2002
Starting with the destructive San Francisco earthquake in 1909, California
has been an incubator for the application of high precision geodetic
measurements. Scientists at NGS and its predecessor agency, the Coast and
Geodetic Survey, have been very active in this arena.
Geophysical scientists have led the development of GPS geodesy for the study
of crustal deformation and earthquakes in California, first by field surveys
(starting in mid 1980’s), then by continuously monitoring stations. One of the
first regional CORS network in the world (the Permanent GPS Geodetic Array)
was established in southern California in 1990.
The destructive 1994 Northridge earthquake spurred a significant increase in
GPS monitoring stations in southern California and led to the establishment of
the Southern California Integrated GPS Network (SCIGN).
Along with similar efforts in northern (BARD array) and eastern California
(BARGEN array), the number of CORS sites in the state is more than 350. The
geophysical community is seeking to more than double the number of CORS
stations in California through NSF’s EarthScope/PBO Project.
History of CORS in California
Y. Bock, CORS Users Forum, April 19, 2002
Southern California Integrated GPS Network
(SCIGN)
SCIGN is at the forefront of
high precision continuous GPS
measurements of crustal
deformation with innovations in
site instrumentation, stable
monuments, data analysis,
archiving and dissemination.
Deformation in
CaliforniaThe position time series on the left
shows the north position component
of the SCIGN site at Pinemeadows
(ROCH) changing by almost 200
mm over a 10-year interval. Each
point represents a 24-hour solution
of GPS data sampled at a 30 s
sampling rate. The filtered time
series (minus regional common-
mode signature) is modeled by three
linear trends discontinuous at
Landers and Hector Mine
earthquakes, three coseismic offsets
(Joshua Tree, Landers, Hector Mine
earthquakes), two postseismic
decays (Landers and Hector Mine),
an annual term, and one equipment-
change offset. The weighted rms is
only 1.2 mm.
Tectonic Motion in Southern California
Southern California
is the location of the
plate boundary
between the North
America and Pacific
plates. The map
shows the motion of
the SCIGN sites
with respect to the
North America,
including a total
motion of about 45
mm/yr across a
region about 200
km wide with
numerous geologic
faults. Determining
the architecture of
faulting and
distribution of
strain is critical for
earthquake studies.
Subsidence in California
#
NEW ORLEANS
Geysers
Uplift
Sacramento
Santa Clara
Caldera Valley
Uplift
Los Banos-Kettleman City
Tulare-W asco
Arvin-Maricopa
Lancaster
Long Beach
San Jacinto
Imperial
Valley
Cascades
California is also “blessed”
with large areas of vertical
motion due to fluid
extraction (water, oil), and
volcanic deformation.
Y. Bock, CORS Users Forum, April 19, 2002
California also relies on
other technologies to
monitor crustal motion, but
these also depend in some
way on C�ORS. In this
example, large areas in the
Los Angeles and Orange
Counties becomes inflated
in April which is consistent
with water table
measurements and the end
of the rainy season. The
spatial pattern of the
amplitude of the annual
signal (solid yellow contours
in mm) derived from SCIGN
sites is consistent with the
shape of the interferometric
SAR fringes (black/white
image). Each fringe
represents about 28 mm of
motion in the line of sight to
the satellite.Reference: Watson et al., Journal of
Geophysical Research, in press, 2002.
Vertical motion in Southern California
Scripps Orbit and Permanent Array Center
(http://sopac.ucsd.edu)
SOPAC is the largest archive
of continuous GPS data and
data products with about 950
sites from around the world
collected every day, including
about 350 CORS sites in
California.
Y. Bock, CORS Users Forum, April 19, 2002
SCOUT: SOPAC Coordinates Update Tool(http://sopac.ucsd.edu/cgi-bin/SCOUT.cgi)
Y. Bock, CORS Users Forum, April 19, 2002
UNAVCO GPS Seamless Archive:
Map of GPS Data - Western U.S.
Y. Bock, CORS Users Forum, April 19, 2002
California Spatial Reference Center“Providing California’s geodetic framework for scientific,
surveying, engineering, and geographic information systems”
Mandate (in partnership with NGS):
Provide the necessary geodetic services to ensure
the availability of accurate, consistent, and timely
spatial referencing data.
Establish the legal spatial reference system for
California.
Monitor temporal changes in geodetic coordinates
due to tectonic motion, volcanic deformation and
land subsidence.
Y. Bock, CORS Users Forum, April 19, 2002
The surveying/engineering community in California has worked
with and supported the geophysical scientists in GPS measurements
of crustal deformation. Surveyors in southern California (Riverside,
Los Angeles, San Diego, and Orange Counties) have been at the
forefront of this collaboration.
A group of surveyor activists started a grass roots movement to
leverage the GPS infrastructure established for earthquake
research as the basis for defining and maintaining a statewide
geodetic reference frame. They felt that California had special
geodetic needs because of its tectonic setting, extensive land
subsidence, and natural hazards, along with one of the largest
economies in the world. This effort eventually coalesced into the
California Spatial Reference Center. This group has unselfishly
promoted the CSRC for the past several years and has started
educating the public on its benefits.
The CSRC organized itself into a Coordinating Council with
representatives of all the relevant agencies and organizations in
California (more than 40) and an Executive Committee.
History of the CSRC
CSRC Highlights
CSRC leverages ~$25M investment in geophysical science
infrastructure over the last decade (includes SOPAC).
Operational center dedicated at University of California San Diego‟s
Scripps Institution of Oceanography in February, 2001.
CSRC is now an official UCSD Support Group (Bylaws approved as
part of process).
Significant increase in funding in FY „01 ($1M from NGS) for height
modernization and real-time GPS positioning networks ($80K from
Orange County).
$1M FY‟02 funds in NGS budget for CSRC. Caltrans funding for
CORS/HPGN ITRF2000/NAD83 analysis, and CORS infrastructure.
Y. Bock, CORS Users Forum, April 19, 2002
CORS coordinates and velocities computed by CSRC are
sanctioned by NGS and are the legal basis for surveying in
California.
Work jointly to provide seamless links between the databases of
the California Spatial Reference Center (CSRC) and the NGS, and
to make NSRS data and CSRS data available to users.
CSRC maintains a secondary archive of the national CORS for
NGS, and work cooperatively with NGS to archive CORS data
collected in North America (including Canada and Mexico).
Cooperate in the preparation and publication of the NAD 2004
and in the production of velocity maps for use in the Horizontal
Time Dependent Positioning (HTDP) model.
NGS and CSRC Partnership
Y. Bock, CORS Users Forum, April 19, 2002
CSRC Master Plan
The CSRC has developed a
Master Plan a 4-D spatial
reference network for height
modernization and geodetic
control in California that
includes a mix of CORS and
traditional geodetic monuments
along transportation corridors.
The actual implementation will
probably depend on
technological developments such
as wide-area RTK, real-time
networks, and wireless
communications.
Y. Bock, CORS Users Forum, April 19, 2002
Commercially driven
High productivity
Continuous real-time access to data
High sampling rate (1-5 sec)
Near real-time processing
Static datum
Scientifically driven
High accuracy
Daily to hourly access to data
Low sampling rate (30 sec)
Post processing
Dynamic datum
GeophysicsSurveying
Although CORS are very useful for both the surveying and
geophysics communities, the requirements have been different as
illustrated in the bullets above. New GPS analysis techniques such
as instantaneous (epoch-by-epoch) positioning have demonstrated
the usefulness of high-rate, real-time requirements for geophysical
science (see next three slides).
Y. Bock, CORS Users Forum, April 19, 2002
Measuring Seismic Ground Motion with CORS
The 1999 Mw=7.1 Hector
Mine earthquake (star
denotes epicenter) caused
significant ground motion
(dynamic and permanent)
over much of southern
California. The contours
indicate the amount of
horizontal ground motion
induced by the earthquake (in
mm). The arrows show the
direction of motion. The black
diamonds indicate a subset of
SCIGN sites active during the
earthquake.
Y. Bock, CORS Users Forum, April 19, 2002
Observed and modeled ground
displacements along the north-
south SCIGN profile in north
(blue asterisks and line) and east
(green asterisks and line) for 120
seconds after the earthquake.
Instantaneous 30 s coordinates
of the sites were estimated
relative to LDES, closest to the
epicenter. Sites are in the order
of closest (top) to farthest
(bottom) from the epicenter. Note
the excellent match between
observed and modeled
displacements, in particular the
2nd and 3rd set of measurements
after the earthquake at sites
WIDC (74 km from epicenter),
PIN1 (110 km) and MONP (189
km).
Measuring Seismic Ground Motion with CORS
Y. Bock, CORS Users Forum, April 19, 2002
North and East
displacements of the
SCIGN sites in the Los
Angeles basin for the 20
minutes centered on the
Hector Mine earthquake.
Clearly, the GPS record
show large amplitude
ground displacements
lasting for more than a few
minutes at some locations
in LA. It is likely that lower
frequency signals may be a
significant contributor to
the overall ground
displacement. Seismic data
is usually restricted to
several seconds after the
event.
Measuring Seismic Ground Motion with CORS
Y. Bock, CORS Users Forum, April 19, 2002
CSRC 2001 Projects
Funded by NGS
California Spatial Reference Network Master Plan
Orange County Real-Time GPS Network
CSRC Data Portal Development
NAVD88 Height Derivation on CORS
South San Francisco Bay Height Modernization
Interferometric SAR (InSAR) and Height Modernization
Y. Bock, CORS Users Forum, April 19, 2002
Orange County Real-Time Network
RTK Web Service for Orange County‟s Geomatics/Land Information Division of the County's Public Facilities and Resource Department (PFRD).
Wireless radio telemetry for the 1 Hz real time data stream from 12 SCIGN/CORS sites.
Capture data on server. QC data and transfer via TCP/IP to CSRC/SOPAC in real-time (1 sec latency).
Testing Leica’s CRNet and Trimble’s VRS software.
Y. Bock, CORS Users Forum, April 19, 2002
Orange County Real-Time Network -
County-Wide RTCM Web Server
RTCM server will provide RTK data via TCP/IP sockets.
Wireless Web access to RTCM server.
Eliminate the need for a local RTK base stations and provide a common datum.
Determine in-the-field orthometric heights by providing a geoidal model and a corrector surface.
Position dynamic objects in real-time.
Y. Bock, CORS Users Forum, April 19, 2002
Some Real-Time CORS Applications
Surveying and Precise GIS
Emergency Services
Landslide warning systems
Dam and bridge deformation
Vehicle tracking, automated highways, intelligent transportation
Aircraft landing and harbor approach
Machine control
Y. Bock, CORS Users Forum, April 19, 2002
Dam Deformation:
Diamond Valley Lake
Largest water reservoir in
southern California
Three earthen dams
7 GPS receivers sampling at 2
seconds
Maximum distance 8 km
Data streaming by radio
modems
Real-time network solution
Raw data and photo courtesy of Mike Duffy and Cecilia Whitaker, Metropolitan Water
District of Southern California
Y. Bock, CORS Users Forum, April 19, 2002
More Real-Time GPS Networks
OCRTN is a prototype for
other installations within the
State such as Western
Riverside County (below) and
the SF Bay Area (to the left).
Southern California
Real-Time GPS Network
Real-time upgrades of
SCIGN will take
advantage of high-speed
communications
infrastructure developed
at UCSD‟s
Supercomputer Center
(SDSC) and Scripps for
seismic and other
scientific data.
Y. Bock, CORS Users Forum, April 19, 2002
Present/Future of CORS in California
Ongoing conversion of GPS arrays to real-time
Densification by CSRC and PBO
Use of these arrays by the public, e.g. SCIGN/ California Spatial Reference Center – Orange County
Proliferation of precise real-time applications
Enhanced real-time communications; wireless Internet (3G) and/or satellites
Development of Web Services based on modern IT methods, for dissemination of data and metadata.
Three-frequency satellite constellation: GPS+, GLONASS, European Galileo
Multi-frequency measurement engines < $0.5 k
Y. Bock, CORS Users Forum, April 19, 2002
Plate Boundary
Observatory (PBO)
New sites:
•Backbone and clusters:•Alaska and Cascadia
•Volcanic complexes
•San Andreas fault zone
Existing sites:
•PANGA, BARD, EBRY,
BARGEN, LVC, SCIGN